2 hole pizzas equal 16 because 1 pizza has 8 slices so make 1/4 a decimal which is 4 4/16 equals 4 so for 4 friends 1/4 is left and do the same to the 21/3 which equals 7 so 7 +4 = half the amount to fead the friends
42,600 - 25,800 = 16800. That is the increase in 15 years.
You then calculate the increase as a percentage of the original population; 25,800.
16,800 / 25,800 * 100 = 65.11%